What’s been killing honeybees by the hundreds of thousands in Northern California has been a mystery, but a report published in January from an eight-year study in Butte and Tehama counties' almond orchards say two combined chemicals were partially responsible.

The study found combinations of insecticides and fungicides, alone benign to bees, are toxic, according to the study’s lead researcher, Reed Johnson, professor of entomology at Ohio State University and an expert on pollinator toxicology.

“When a study comes out like this, we know how critical it is," said almond grower Rory Crowley, co-owner of the Nicolaus Nut Company in Chico. “Almond growers see bees as a critical collaborator. It’s in our best interest to keep the bees as healthy as possible."

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Crowley’s family-owned company rents bees from North State beekeepers every year to pollinate its 150 acres of almonds in and around Chico.

The Almond Board of California has followed Johnson's findings closely since his study began in 2011. That’s when bees began to die off at alarming rates in California almond orchards.

“The queen breeders were experiencing death" of their offspring,” Johnson said. “That’s what brought me to Chico in 2011."

Johnson found that a pesticide, which didn’t harm adult bees, hurt or killed their young, he said.

The worst bee die-off was in 2014, Johnson said. About 80,000 colonies suffered “significant adult deaths" and produced deformed brood. About 1.5 million bee colonies pollinated California’s almond production that year.

The study also linked bee deaths, in part, to applying chemicals to almond blossoms while bees are active, Johnson said. “Every time an applicator uses a pesticide, it’s recorded in the California Department of Pesticide database,” then released to the public.

“No other state does that. It’s only because of this transparent pesticide reporting” we found the cause, he said. “2014 was the top year for pesticide application.”

The Almond Board of California also helped fund Johnson's work as soon as growers found out about it, board spokesperson Bob Curtis said. Access to the study's early research enabled the board to recommend new policies years before the findings were published.

“We put together a best management practices pamphlet” for growers, beekeepers and those who apply chemicals, Curtis said. “We did a really extensive outreach (education) program."

Response was almost immediate, Johnson said. “In 2015, insecticide use dropped to about half” of the amount used in 2014.

A beekeeper sets up a hive in an almond orchard. Almond growers rent bees to pollinate their trees when they bloom.(Photo: Almond Board of California)

Now the standard practice is to wait until bees stop flying before you apply particular chemicals to almond trees, Crowley said. That means growers avoid using chemicals when outside temperatures reach 54 degrees — the temperature needed before bees will fly out of their hive.

“That was the most satisfying thing out of this project,” Johnson said. "It appears that working with the almond board got the word out. Time will tell if it really solved the problem, but it appears to be a really simple change.”

Beekeepers face tough times

Johnson said bee die-offs are still a serious problem nationwide. “This is just one small issue that we got worked out. We’re not out of the woods yet.”

Beekeeping is a high-risk business, Johnson said. Besides pesticides and other chemicals, causes of bee death and illness include parasites that transmit viruses, problems stemming from drought and other issues.

Jared King and his wife Kelsey opened the Jefferson Bee Co. in 2016 out of their home in Red Bluff. They rent most of their 200 to 300 hives, each of which contains as many as 40,000 to 50,000 bees, to almond growers in and around Gerber, King said.

The 2017 and 2018 die-offs hit them hard, King said. Varroa mites were a primary factor. “We lost roughly 70 percent (of our bees). Almond contracts were hard to fulfill.”

Bees bolster big biz

California almond growers supply about 80 percent of the world’s almonds according to the almond board. The almond industry generates more than $21 billion in revenue.

Almonds usually blossom from February to March in California's Central Valley.(Photo: Almond Board of California)

Johnson’s study said 1.48 million honeybee colonies spent February 2017 in California’s almond groves, pollinating trees to the tune of more than $253 million. In 2018, bee-rental costs were up to almost $3 million.

Growers are receptive to helping beekeepers, and the two rely on each other, King said. “Our bees only benefit from being in the almonds. They go crazy on the pollen."

Pollen is sort of raw baby food for bees. Adult bees process the pollen in their bodies, then feed it to their young, King said.

In the North State, queen bees typically lay eggs from January to October, but spring is when they’re most productive, King said. That’s why February's pollen-rich almond blossoms are a hit with bees. More baby bees means more adult bees making honey.

“The main honey flow starts in July,” he said.

Honeybees are responsible for pollinating 80 percent of produce grown in the U.S., Johnson said. “The more nutritious foods in our diet rely on bees.” If they died out “we’d be less healthy for sure.”